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>Chapter 5. Principles of Operation</H1
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>			Cacti operation may be divided into three different tasks:
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>Figure 5-1. Principles of Operation</B
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>				First task is to retrieve data. Cacti will do so using its Poller.
				The Poller is executed from the operating system's scheduler,
				e.g. crontab for Unix flavored OSes.
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>				In current IT installations, you're dealing with lots of devices
				of different kind, e.g. servers, network equipment, appliances
				and the like. To retrieve data from remote targets/hosts,
				cacti will mainly use the Simple Network Management Protocol SNMP.
				Thus, all devices capable of using SNMP will be eligible to be
				monitored by cacti.
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>				Later on, we demonstrate how to extend cacti's capabilities of
				retrieving data to scripts, script queries and more.
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